ScienceShot

ScienceShot: Lonely Plant Enlists Ants

On two vertical cliffs in the Pyrenees Mountains between France and Spain, 1000 or so puny, yamlike plants cling to life—and despite the plant's precarious cliffside existence, it somehow manages to reproduce. The plants, described by an alpine gardening Web site as "essentially modest foliage plants and mainly for the connoisseur," are all that's left of the species Borderea chouardii,a holdover from an otherwise vanished tropical ecosystem. Scientists suspected insect visitors carried pollen between the separate male and female plants, so with help from scaffolding and climbing gear, they spent 76 hours monitoring the plants in 2008 and 2009. Mostly, they saw ants. They ruled out wind pollination by setting out slides, then checking the pollen that collected on them. Then, through a series of experiments where they offered seeds to ants, they worked out that different species of ants were sharing the labor: Two species of ants pollinate the flowers and a third disperses the seeds, the team reports online today in PLoS ONE. However, the scientists note, relying on another species is risky, so how do the plants get away with putting all of their reproductive eggs in a few ant-carried baskets? One possibility is that the plants don't have to put out a lot of seed because they live so long—more than 300 years. And it probably helps that big herbivores can't reach them on their clifftop dwellings.